I have a fairly diverse mix of cars that I drive routinely. My diesels are 67 and 120hp (I drive the 120hp car more as the 67hp car is like new and I'm keeping it that way). My one BMW is 134hp and the other is 300hp.
I can get almost 30mpg routinely in my 300hp 135i, and have had excursions up to nearly 32mpg. Just because you have a fast car doesn't mean that you HAVE to drive it that way. If done right, like the BMW, high fuel economy can be had too.
I've routinely said that one really only needs 120-130hp, and I believe that is true. If driven that way, economy and fun can be had, and it doesn't wear off. Any time I hit WOT on the 135, and the speedometer flies up faster than I can see, I get a smile on my face. The convertible helps a lot. I'm top down better than 50% of the time, even when cold.
That said, driving my E30 around curves, or hearing my diesel turbo spool up brings enjoyment too.
I'd say to be reasonable though too. If I only had, say, my 135i, I'd probably be vying for more space sometimes. That said, having a lot of cars, I find there is somewhat of a stress level from thinking about which is outside in what weather, etc. However, I'm still an advocate of having lower economy vehicles or less utilitarian vehicles having a brother, to use in poor weather, expensive fuel conditions, etc.
